Benzidine, preparation

The submitters used benzidine obtained by neutralization of an aqueous solution of c.p. benzidine dihydrochloride (Mathe-son, Coleman and Bell) with 20% sodium hydroxide solution, followed by crystallization from 60-70% ethanol. The benzidine prepared in this manner was in the form of light tan flakes. Freshly prepared benzidine should be used for the best results. 

It is prepared by reduction of nitrobenzene with iron and NaOH. It is also prepared by an electrolytic reduction of nitrobenzene. It is widely used for the preparation of benzidine. 

Required Hydrazobenzene, lo g. zinc dust, lo g. HYDRAZOBENZENE. The above preparation of benzidine... 

This dyestuff is prepared by tetrazotisiiig benzidine and coupling with sodium naphthionate ... 

N,N -Diethylbenzidine has been prepared by heating ethyl iodide, benzidine, and ethanol in a pressure tube at water-bath temperature, and by the reaction of diethylzinc on benzene-diazonium chloride. The method described here is a modification of that of Shah, Tilak, and Venkataraman. ... 

The benzidine rearrangement is of interest for mechanistic considerations. The preparative applicability may be limited because of the many side products, together with low yields. Furthermore benzidine is a carcinogenic compound. ... 

Difluorobiphenyl has been prepared from 4,4 -biphenyl-bis-diazonium piperidide (by diazotizing benzidine and coupling with piperidine) and concentrated hydrofluoric acid 1 by the action of sodium on -fluorobromobenzene in ether 2 from benzidine by tetrazotization and decomposing the biphenyl-bis-diazonium salt with concentrated hydrofluoric acid 3 by the above method in the presence of ferric chloride 4 and by the prolonged contact of the vapors of fluorobenzene with a red-hot wire.5 The method described here is the most satisfactory for... 

Add 5 ml of sodium hypochlorite (Clorox) to 50 ml of acetic acid prepare the benzidine solution by dissolving 0.5 g of benzidine and one crystal of KI in 50-ml ethanol-HjO (1 1) spray the plates with the Clorox reagent and let dry then spray with benzidine reagent... 

Since their commercial introduction during the 1940s as components of proprietary detergents and laundry preparations, these products have found extensive usage in the whitening of paper and textile materials. Disperse FBAs are available for whitening hydrophobic fibres and solvent-soluble FBAs impart fluorescence to oils, paints, varnishes and waxes. Approximately 75% of commercially established FBAs are stilbene derivatives with inherent substantivity for paper and cellulosic textiles, but the remainder come from about twenty different chemical classes. These include aminocoumarins (6%), naphthalimides (3%), pyrazoles and pyrazolines (each about 2%), acenaphthenes, benzidine sulphones, stilbene-naphthotriazoles, thiazoles and xanthenes (each about 1%). FBAs of these and other chemical types are discussed in detail in Chapter 11 of Volume 2. 

Quinone may be prepared by the oxidation of aniline with dichromate or manganese dioxide and sulfuric acid.1 This is a more feasible commercial method than the one given. However, the oxidation of hydroquinone is more rapid and convenient and, hence is more desirable for use in the laboratory. Various materials have been oxidized by chemical means to give quinone they are quinic acid,2 hydroquinone,3 benzidine,4 -phenylene-diamine,5 sulfanilic acid,6 / -phenolsulfonic acid,7 arbutin,8 aniline black,9 and the leaves of various plants.10 Quinone is also formed by several other methods by the fermentation of fresh grass 11 by the action of iodine on the lead salt of hydroquin-... 

Nucleophiles, when they are used in the presence of cupric perchlorate, capture the cation-radicals initially formed. Instead of benzidines, the para-substituted dialkylanilines were obtained. In this a manner, A,A-dialkylanilines with halo or thiocyanato moieties in para positions were prepared in good yields under the same (simple) conditions. Scheme 7.13 illustrates the sequence of the transformations observed. The products are useful intermediates in the synthesis of dyes, drugs, and color cinema formulations. 

Procedure. A primary standard solution of benzidine in methanol was prepared. Standards of lower concentrations were prepared by dilution of the primary standard. Typical liquid chromatograph calibration curves were linear in the region from .38 to 30.6 yg/mL. The standards were stable for several months when stored in the dark. Aqueous solutions of known dye-formulation concentration were prepared. 

The spiked filters were placed in a 50-mL beaker with the spiked side up and 1 mL of water was added. The beaker was shaken so that all of the filter area had been washed by the water. One mL of the reduction-buffer solution without the sodium hydrosulfite was added to the filter and water. The beaker was shaken a second time. The filter was then turned over (spiked side down) and the beaker placed in an ultrasonic bath for 15 minutes. At the end of this period, the solution in the beaker was colored. A 1-mL aliquot of this solution was transferred to a 4-mL vial. One mL of a freshly prepared solution of 100-mg sodium hydrosulfite in 10-mL phosphate reduction buffer was then added to the vial. The vial was then capped and shaken several times during the course of an hour. During this time, the original color of the solution disappeared or changed to a different color, depending on the dye present. This solution was then injected into the liquid chromatograph. A 10-yL aliquot was used, giving a measurement limit of 0.38 ng benzidine/yL. The analytical reproducibility at this limit was 10% coefficient of variation (CV). 

Hasegawa et al. (1) prepared conjugated pyromellitic dianhydride polyazo-methines, (I), and converted them into a pyromellitic polyimide ladder, ( ), by reacting with two equivalents of benzidine. 

An example of a yellow sulfur dye is Immedial Supra Yellow GWL which may be prepared by thionation of a mixture of benzidine and dehydrothio-p-toluidine. Zerweek and coworkers suggested the structure consists of four dyes but a more recent degradative study indicates that the major component is (26) (62CCC1533). 

Polybenzimidazols developed for heat-resistant resins were also applied to reverse osmosis membranes, first by Cellanese Corporation 67 68). The asymmetric poly-2,2 -(m-phenylene)-5,5 -dibenzimidazole membrane 18 was prepared from 3,3 -diamino-benzidine (79) and diphenyl isophthalate (20) and had a high water flux permeability,... 

These substances were prepared by Mertens89 in 1886 by the action of nitric acid on dimethylaniline (I, II, and III) and on monomethylaniline (II and III). Van Romburgh90 in the same year proved them to be derivatives of benzidine, and at a much later time91 summarized the work which had been done upon them and synthesized the substances in such manner as to prove the position of the nitro groups. 

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